Catheters are used to access treatment sites within the body by guiding the catheter through body cavities, ducts or vessels to the target site. Catheters have several uses in medicine and surgery and may be used to increase the diameter of a narrowed vessel (such as by using a balloon catheter to expand blood vessels), open Chronic Total Occlusions (CTO) in vessels, or ablate tissues using a high-energy source. The advantage to using a catheter for patient treatment is that the catheter allows the practitioner to target regions within the body by using minimally invasive techniques. To first reach the target location, a practitioner places the catheter through a small opening of a patient (such as a blood vessel) and guides the tip of the catheter through the vasculature until the tip reaches the desired target location within the body. Once the tip of the catheter is at the target site, the practitioner can use a variety of techniques to deliver treatment to the patient via the catheter tip.
Several conditions and diseases can be treated using catheters. For example, several heart rhythm disorders can be treated by using catheters that emit high-energy waves, or contain tissue freezing cryogenic fluid, at the tip of the catheter to ablate cardiac tissue causing the aberrant condition. Aberrant conditions include cardiac arrhythmias, such as Atrioventricular nodal reentrant tachycardia (AVNRT), Atrioventricular Reciprocating Tachycardia (AVRT), atrial fibrillation, atrial flutter, and ventricular tachycardia, to name a few.
Safe, effective catheters that are used to treat atrial fibrillation are highly desired because millions of people worldwide have are afflicted with this condition. Although ablation procedures using a catheter have great potential, however, the long-term success rate for ablation has not risen above at 50-60%. This long-term success rate has been partly attributed to the inability to permanently isolate the pulmonary veins. This inability to isolate pulmonary veins, and other target regions, are one of the many problems faced by practitioners using present-day catheters. The inability to effective target treatment locations is often due to the lack of stability of the catheter (i.e., the inadvertent movement of the catheter during use). The lack of stability is partly due to the required flexibility of the catheter to reach the target site.
An ideal catheter must be flexible enough to be steered within the vasculature of the patient, however, if too flexible, the catheter will likely buckle and not advance properly. The stiffer the catheter, the more stable the position, however, a stiff catheter has several other problems. First, if it is too stiff, the catheter will not be able to make the tortuous turns in the vasculature to reach the treatment site, and second, a stiff catheter is more likely to damage delicate tissues within the patient.
Specifically for the treatment of a rhythm disorder, catheters are first introduced into the body via a vein or artery and then guided under fluoroscopic or magnetic guidance to relevant regions of the heart to diagnose the cause of this abnormal rhythm. To treat this abnormal rhythm, one technique is to ablate the responsible tissue in the heart. When the tissue is ablated, the correct heart rhythm is hopefully restored. To ablate the cardiac tissue, the practitioner uses a catheter having a deflectable tip that the practitioner is able to direct by using tension wires within the catheter to aim the tip toward the target tissue. When the tip is at the desired location, the practitioner uses the catheter to deliver energy, which ablates the tissue. The technique of energy delivery includes but is not limited to radiofrequency, cryogenic tissue freezing tissue and laser beams.
While in theory the tip of the catheter that emits high energy is pointed only at the tissue that should be ablated, the catheter may move during any number of steps of the procedure. For example, the catheter may move while the practitioner obtains intra-cardiac electrogram, cardiac pacing, or during ablation itself. Repositioning the catheter can be both time consuming, frustrating, and prevent successful ablation. It can also potentially cause complications if the catheter moves during ablation because if the catheter moves during ablation, the wrong cardiac tissue may be ablated and damage the normal conduction pathways needed for proper heart functioning or even cause structural damage including perforation of the heart tissue.
There have been several attempts to increase stability of the catheter. One way to increase stability is the use of long, deflectable sheaths. However, these sheaths can be cumbersome, with higher potential of thrombosis within sheathes. Another way to increase stability is the use of remote navigation systems. However, remote navigation systems have high initial startup as well as ongoing costs and are cumbersome to use, thereby preventing widespread adoption.
Therefore, it would be beneficial to provide a catheter that has sufficient flexibility to be easily manipulated, be stiff enough to maintain its shape once a target location is reached, not require sheath exchange, have inexpensive startup and operation costs, and be usable with currently available and installed technologies.